Field discharge breaker



Jan. 31,1967 G. A. WILSON v 3,301,985

' FIELD DISCHARGE BREAKER Filed March 1965 4 Sheets-Sheet 1 id- I I i 32 36 f 1 37 0 4. 5 3 75.40 swea 4 l '1 MA O/A/f 3 o7 [3 i 33 V o w- E INVENTOR.

J 1957 G. A. WILSON FIELD DISCHARGE BREAKER Filed March 2, 1965 INVENTOR. L 4:42;: ,4, MLSOA/ 4 Sheets-Sheet 2 Jan. 1967 G. A. WILSON v FIELD DISCHARGE BREAKER F1 led March :1, 1965 4 Sheets-Sheet '3 W INVENTOR.

47mg; 4. 14/4 d/x G. A. WILSON FIELD DISCHARGE BREAKER.

Jan, 31, 1967 Filed March 2,, 1965 4 Sheets-Sheet INVENTOR. 620 246 4. MZSU/l/ fraZA (FKS United States Patent C) 3,301,985 FIELD DISCHARGE BREAKER George A. Wilson, Media, Pa., assignor to ll-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 2, 1965, Ser. No. 436,468 6 Claims. (Cl. 200153) The instant invention relates to circuit breakers in general, and more particularly to a field discharge circuit breaker having a novel construction which achieves a more reliable coordination between the circuit breaker contacts and field discharge contacts than has heretofore been possible.

The instant invention further provides novel means for use in controlling overlap between the discharge switch and main contacts so as to always provide overlap during opening operation and to alternatively provide a choice of overlap or no-overlap during a closing operation.

In an energized D.C. motor, or generator, if the field circuit thereof is suddenly opened, then owing to the rapid decrease of flux through the large number of field coil turns, a large will be induced between the two open ends. This may be sufiicient to break down the insulation between the field coils and pole pieces. To prevent this, a resistor is permanently connected in parallel with the field coil or else a resistor is switched in parallel with the field coil when the energizing circuit to the field is opened.

It is essential that the switching of the discharge resistor be precisely coordinated with the switching of the field coil energizing circuit. To this end, a field discharge circuit breaker is provided which include two pairs of circuit breaker contacts for switching the energizing circuit of the field coil and another pair of contacts for switching the field discharge resistor. That is, the field discharge resistor is connected to short circuit the field coil an instant before the circuit breaker contacts open and is disconnected from short circuiting the field coil an instant after the circuit breaker closes.

Field discharge circuit breakers of the prior art did not provide a precise timing between the circuit breaker contacts and field discharge contacts. Further, the adjustments thereof were very difiicult to achieve. The flexing of the circuit breaker components caused by their own inertia contributes to undesirable variations in the contact sequence. Further, when the opening speed of the circuit breaker changed because of the changes in the magnitude of current flowing through the circuit breaker, its coordination with the field discharge contacts was upset.

The instant invention further provides a movable discharge contact having a cam means rigidly coupled thereto. This cam means is provided with a cam surface, which slidingly engages a roller member coupled to the field discharge switch operating mechanism to operate the cam means and hence the discharge switch movable arm between its connected and disconnected positions.

The cam means is further provided with a second pivotally mounted cam means which is designed to cooperate with the first cam means cam surface to provide overlapping closure between the discharge switch contacts and the main contacts during the opening operation.

During a closing operation, however, the second cam means may optionally be employed to provide either overlapping or non-overlapping contact closure with the main contacts, depending upon the needs of the user. In the case where no overlapping closure between the discharge contacts and main contacts i desired, the roller which slidingly engages the cam surface of the first cam means has coupled thereto a lever which abuts the second contact means while the roller is still in sliding engagement surface, so as to verge the second contact means cam surface to prevent sliding engagement with the roller member. This causes the field discharge switch to open prior to the main contacts closing.

In the case where overlap between the main contacts closing and the discharge switch contacts opening is desired, this may be done simply by inserting a pin member in an opening provided therefor in the first cam means to abut one edge of the second cam means, thereby preventing it from moving away from the roller member and causing the roller member to make sliding engagement with both the first and second cam means cam surface. The lever means may also be completely removed so as to prevent the lever from making any engagement whatsoever with the second cam means. If a modification from an overlap condition to a no-overlap condition is desired, this may be done simply by removing the two pins referred to above.

It is, therefore, one primary object of the instant invention to provide a novel discharge switch mechanism for use in field discharge circuit breakers and the like.

Another object of the instant invention is to provide a novel discharge switch mechanism for use in field discharge circuit breakers and the like, wherein novel first and second cam means are employed to provide overlap between the discharge contacts and the main contacts of the field discharge breaker.

Still another object of the instant invention is to provide a novel discharge switch mechanism for use in field discharge circuit breakers and the like, wherein novel first and second cam means are employed to provide overlap between the discharge contacts and the main contacts of the field discharge breaker on opening, and to provide the optional arrangement of either an overlap or no-overlap between the main and discharge contacts during the closing operation.

These and other objects of the instant invention will become apparent when reading the accompanying description and drawings, in which:

FIGURE 1 is a perspective view of my novel field cir cuit breaker;

FIGURE 2 is a circuit diagram illustrating one manner in which a field discharge circuit breaker may be connected in a circuit to protect the field winding of a DC. motor;

FIGURE 3 is a side elevation of the field discharge circuit breaker discharge switch showing the field discharge circuit contacts in the closed positions;

FIGURE 4 is a side elevation of the field discharge circuit breaker discharge switch showing the field discharge circuit contacts in the open position;

FIGURE 5 is a side elevation of one of the main contacts of the field discharge circuit breaker of FIGURE 1, showing the main contacts in the closed position in dotted fashion and showing the main contacts in the open position in solid line fashion.

Referring now to the drawings and, more particularly, to FIGURES 1 and 2, field discharge circuit breaker 20 comprises circuit breaker, or main poles 21 and 22 and field discharge pole 23 which is positioned therebetween and isolated therefrom by interphase barrier 24. Main poles 21, 22 are provided with are chutes 26, while field discharge pole 23 is provided with a separate arc chute 27.

Jack shaft 60 provides a direct mechanical connection between main poles 21 and 22 so that these poles operate in unison. Operation of main poles 21, 22 is customarily accomplished by means of solenoid assembly 28 which may be any one of the many conventional constructions known to the art. Handle 29 mounted on escutcheon 30 is provided for manual operation.

When circuit breaker is connected to protect the field winding 31 of a DC motor, main poles 21 and 22 are each connected in series with an individual line connecting field winding terminals 32, 33 to terminals 34, 35, respectively, of DC. power source 36. Field discharge pole 23 is connected in series with discharge resistor 37 and this series combination is connected between the winding terminals 32, 33. The operation of field discharge pole 23 is coordinated with that of circuit breaker poles 21, 22, in a manner to be hereinafter explained, so that upon energizing winding 31, circuit breaker poles 21, 22 close and an instant thereafter field discharge pole 23 opens. Upon deenergizing winding 31 field discharge pole 23 closes an instant before circuit breaker poles 21, 22 open. Thus when poles 21, 22 open the electrical energy stored in winding 31 is confronted by the relatively low impedance of resistor 37 thereby preventing the buildup of excessive voltages between the winding terminals 32, 33.

Referring now to FIGURE 5, the main poles 21 and 22 each comprise substantially identical exemplary structures. Therefore, only one main pole unit 21 shall be described.

Pole unit 21 includes a contact arm 40 pivotally mounted to the frame at 41. Contact member 42 is mounted to contact arm 40 and is arranged to cooperate with pivotally mounted contact 43 which, in turn, is pivoted at 44.

Contact arm 40 is pivotally secured at to one end of a member or link 56, the opposite end of which is secured at 57 to crank 58, which is coupled to jack shaft arm 59 (which jack shaft is shown in FIGURES 3 and 4). The jack shaft arm 59 is keyed to a substantially heX- agonal shaped jack shaft 60, which is designed to rotate both of the contact arms 40 of main poles 21 and 22.

The operation of the contact arms 40 is as follows:

With the field discharge circuit breaker in the closed position, the jack shaft arm 59 assumes the position shown in FIGURE 3. This places the contact arms 40 of main poles 21 and 22 in the closed position shown by the dotted outline 40. When the hexagonal shaft 60 rotates clockwise as shown by arrow 61, this causes connecting member 56 to move from the dotted line position 56' to the solid line position 56, in turn causing the contact arms 40 to move from the dotted line position 40' to the solid line position 40 as shown in FIGURE 5. Thus, the cooperating contacts 42 and 43 move from the engaged to the open or disconnected position. The contact 43, which is pivoted at 44, is urged in the counter-clockwise direction by biasing means 62 so as to aid in the opening operation and further to urge the cooperating contacts 42 and 43 into firm engagement when the contact arms 40 of the main poles 21 and 22 are in the closed position.

Turning now to the field discharge switch assembly shown in FIGURES 3 and 4, this assembly is comprised of an upper terminal 71 coupled through a connecting assembly 72 to a conductive angle arm 73. The arm 73 is coupled through fastening means 74 to a stationary conductive member 75 which has pivotally connected thereto, at 76, a rotatable contact 77. Contact 77 is provided with a pin 78 linking an arm 79 thereto. Surrounding arm 79 is a helical spring member 80 having a first end bearing against vertical support 81 and a second end bearing against contact 77 at 82. Arm 79 passes through an opening 83 in vertical support 81 and is provided with a stop member 84 to limit the movement of contact 77 as it moves in the clockwise direction about its pivot 76.

A shock absorbing member 85 comprised of an elongated rod 86 is coupled to support 81 and angle member 73 by fastening means 87. The right-hand end 88 of shock absorbing member 85 is designed to lie in the path of discharge switch arm 90 in order to cushion or absorb the closing impact of arm 90.

The discharge switch movable arm 90 is pivoted at 91 and makes electrical engagement through fastening means 92, conductive angle arm 93 and coupling member 94 to a lower terminal 95.

The rotatable arm 90 has coupled thereto a first cam member 96, which is rigidly secured to arm 90 by fastening means 97 and 98. The first cam member 96 is provided with a cam surface 96A, which makes sliding engagement with a roller member 97, to be more fully described. The lower end of rotatable arm 90 is provided with a pin 98 which is fastened to one end of a helical spring 99, the opposite end of which is coupled to fastening means 100. Spring means 99 acts to normally bias the rotatable arm 90 toward the open position shown in FIGURE 4.

A second cam assembly 101 is comprised of a bellshaped member 102 coupled to first cam member 96 by means of pin 103. The counter-clockwise rotation of bell-shaped member 102 is limited by pin 104, which is rigidly secured to first cam member 96. A torsion spring is wound about pin 103 and has a first end thereof bearing against pin 104 and a second end thereof rigidly secured to bell-shaped member 102 at 106. First cam member 96 is further provided with apertures 107 and 108 for removably receiving a pin member which, for example, may be inserted into aperture 107, thus limiting the clockwise rotation which bell-shaped member 102 may undergo relative to the longitudinal axis of pin 103. Removal of the pin 109 from aperture 107 and insertion of this pin into aperture 106 prevents bell member 102 from undergoing any rotation whatsoever, for a purpose to be more fully described.

Hexagon-al shaft 60 has keyed thereto a large rotatable arm 110 having a hexagonal-shaped opening 110A for receiving shaft 60. the upper left-hand corner of member 110 has a pin i111 secured thereto for rotatably mounting roller 97. A lever member 112 is also mounted to pin 111 and is provided with an opening 112A at a first end thereof for receiving one end of reset spring means 120, the opposite end of which is secured to member 110 at 112C. The spring means urges lever member 112 against a pin means 112d secured to member 110 to prevent any clockwise rotation of lever 112. When in this position, the nose 112B of lever 112 protrudes in the manner shown in FIGURE 3 in dotted line fashion.

Turning now to a consideration of FIGURE 4, the rotatable arm 90 of the discharge switch assembly 70 is in the open position. It should be carefully understood that, simultaneously therewith, the movable arms 40 of main poles 21 and 22 are likewise in the open position due to the fact that members 110 and 59 are keyed to hexagonal shaft 60, which controls the operation (i.e., rotation) of these members.

Let it be assumed that a closing operation is desired and that an overlapping condition of the discharge switch is desired relative to the main poles 21 and 22. For such operation, the pin 109 is removed from aperture 107 and inserted in aperture 108.

The closing operation (for the overlapping condition) is as follows:

Hexagonal shaft 60 is driven by suitable means (not shown) in the counter-clockwise direction as shown by arrow 61A. This causes members 59 and 1110 to rotate counter-clockwise relative to the longitudinal axis of shaft 60.

The movable arms 40 of main poles 21 and 22 are urged from the solid line position 40 of FIGURE 5 to the dotted line position 40', to bring cooperating contact surfaces 42 and 43 into engagement, it being understood that movable arms 40 are coupled to the members 59 through a connecting member 56.

Initially arm 90 is: held in the position shown in FIGURE 3 maintaining contacts 77a and 90a closed.

With reference to FIGURE 3,

imultaneously with the movement of arms 40 toward the closed position, member 110 rotates pin 111 counterclockwise relative to the longitudinal axis of shaft 60, causing the roller 97 rotatably mounted on pin 111 to travel along the cam surface 96a of firstcam member 96, maintaining contacts 77a and 90a closed. There is no motion of arm 90 at this time. It should be noted, that so long as roller 97 makes sliding engagement with any portion of cam surface 96a, engagement is maintained between contact surface 77a and 90a.

As roller 97 leaves cam surface 960, it comes into sliding engagement with the cam surface 102a of bell member 102. With lever 112 removed from member 1110 bell member 102 remains substantially stationary and maintains the first and second cam members 96 and 102, and hence the rotatable arm 90, in position to maintain contacts 77a and 90a in engagement. Thus the closure condition between the discharge switch contact 70 and the main pole contacts 42-43 overlap one another.

The member 110 moves still further in the counterclockwise direction causing roller 97 to leave cam surface 102a, thus placing rotatable arm 90' under control of spring member 99. This causes rotatable arm 90 to move its contact surface 90a out of engagement with cooperating contact surface 77a. Spring means 120 resets lever 112 after an opening operation.

Let it now be assumed that a non-overlapping operation is desired. In order to provide non-overlapping operation, pin 109 is removed from aperture 108 and inserted into aperture 107. In addition, lever 112 and reset spring means 120 are mounted as previously described to maintain lever 112 against pin 112d and in the dotted line position shown in FIGURE 3.

Durin a closing operation for the non-overlapping phase, the shaft 60 rotates counter-clockwise in the same manner as previously described, moving the arm 40 of main poles 21 and 22 from the solid line position to the dotted line position 40'.

With regard to the discharge switch, the roller member 97 makes sliding engagement with cam surface 96a of first cam 96. While roller 97 is still in sliding engagement with cam surface 96a, the nose 112b of lever 112 makes engagement with side 1021) of bell member 102 driving bell member 102 clockwise about the longitudinal axis of pin 103. The total clockwise rotation of bell member 102 is limited by the presence of pin member 109 in aperture 107.

With the nose 11217 driving bell-shaped member 102 in the clockwise direction, roller member 97 is prevented from making sliding engagement with cam surface 102a of bell member 102. Thus, while sliding engagement between roller 97 and cam surface 96a holds the contact surface 90a toward contact surface 77a, the prevention of sliding engagement between cam surface 102a and roller 97 allows the cooperating contact surface 77a and 90a to part.

As soon as roller 97 leaves cam surface 96a, rotatable arm 90 is placed under control of spring member 99, which urges the contact surface 90a of rotatable arm 90 away from engagement with cooperating contact surface 77a.

The total closing motion of the discharge switch 90 must occur before thearcing contacts on the main poles part (during the opening operation). Since the speed of the main poles is extremely high in this region due to the contact spring 62, the speed of the discharge switch 70, in closing, is such that ordinary flat face contacts would be wrecked from the impact. The stationary and moving discharge contacts 770 and 90a, respectively, are therefore slanted as shown, for the purpose of minimizing impact and hence preventing destruction thereof. The shock absorbing stop member 85 is necessary to absorb the remaining energy in the discharge switch arm 90.

During the opening operation the shaft 60 is rotated in the direction shown by arrow 61 of FIGURE 3, driving roller 97 initially into engagement with cam surface 102a for closure of contacts 77a and a before opening of the cooperating contacts of poles 21 and 22, the contacts 77a, 90a remaining closed, through the rolling engagement between roller 97 and cam surface 96a, even after opening of the cooperating contacts of poles 21 and 22.

It can, therefore, be seen that the instant invention provides a novel field discharge switch assembly which may be arranged to provide either an overlapping closure condition or a non-overlapping closure condition between the main poles and the discharge switch of the field discharge circuit breaker simply by the positioning of two separate pin members on the first cam member and removably mounting the switch member.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A discharge switch assembly for use in field discharge circuit breakers comprising a rotatable arm pivotally mounted near a first end thereof; and rotatable between a first and a second position; a first contact secured to said arm rotatable near a second end thereof; a second contact positioned to make electrical engagement with said first contact when said movable arm occupies said first position; a rotatably mounted drive member for operating said rotatable arm; said drive member being mounted for rotation at a first end thereof and having a roller member pivotally mounted thereto at a second end thereof; said drive member being rotatable between a third and a fourth position; first cam means secured to said rotatable arm and having a cam surface positioned to slidingly engage said roller member when said drive member rotates toward the fourth position to drive said first contact toward said second contact; second cam means pivotally mounted to said first cam means and having a second cam surface; spring means coupled between said first and second cam means for urging said second cam surface toward a fifth position adjacent one end of said first cam surface to effectively provide one continuous cam surface; said second cam surface slidably engaging said r-oller member when said roller member leaves said first cam surface as said drive member moves toward the fourth position; bias means coupled to said rotatable arm at said first end normally biasing said first and second contacts out of engagement.

2. The device of claim 1 further comprising a second lever assembly mounted in a sixth position on said drive member adjacent said roller member and having a nose positioned to engage said second cam means when said drive means moves toward the fourth position for rotating said second cam surface away from said roller member to prevent sliding engagement therebetween thereby preventing engagement of said first and second contacts.

3. The device of claim 2 further comprising a first pin; said first cam means having an aperture positioned adjacent one ide of said second cam means when said first and second cam surfaces are positioned to for-m one substantially continuous cam surface; said second cam means being substantially prevented from experiencing any rotation when in said fifth position and said first pin is inserted into said aperture.

4. The device of claim 3 wherein said second lever assembly is comprised of a second lever having a nose at a first end thereof and an arm extending away from said nose; said lever being pivotally mounted to said drive member at a point intermediate the nose and arm of said second lever; means coupled between said second lever and said drive member for retaining said second lever in position to abut said second cam means when said drive means moves toward the fourth position; said means being removable to prevent said second lever from rotating said second cam means.

5. A field discharge circuit breaker comprising first and second main poles each having a pair of cooperating contacts; one of said contacts of each pole being mounted to one end of a movable bridge; second and third drive members coupled to an associated movable bridge and the other contact being substantially stationary; a discharge contact switch of the type described in claim 1; a rotatable shaft keyed to first, second and third drive members for rotating said drive members in unison; said main pole cooperating contacts being engaged at the same time as said contact switch when said second cam means is in said fifth position.

6. A field discharge circuit breaker comprising first and second main poles each having a pair of cooperating contacts; one of said contacts of each pole being mounted to one end of a movable bridge; second and third drive members coupled to an associated movable bridge and the other contact being substantially stationary; a discharge contact switch of the type described in claim 2; a rotatable shaft keyed to first, second and third drive members for rotating said drive members in unison; said main pole cooperating contacts being engaged and said contact switch being disengaged when said second cam means is engaged by said nose.

References Cited by the Examiner UNITED STATES PATENTS 2,922,009 1/1960 Pokorny et al 200-153 X ROBERT K. SCHAEFER, Primary Examiner.

H. I. HOHA'USER, Assistant Examiner. 

1. A DISCHARGE SWITCH ASSEMBLY FOR USE IN FIELD DISCHARGE CIRCUIT BREAKERS COMPRISING A ROTATABLE ARM PIVOTALLY MOUNTED NEAR A FIRST END THEREOF; AND ROTATABLE BETWEEN A FIRST AND A SECOND POSITION; A FIRST CONTACT SECURED TO SAID ARM ROTATABLE NEAR A SECOND END THEREOF; A SECOND CONTACT POSITIONED TO MAKE ELECTRICAL ENGAGEMENT WITH SAID FIRST CONTACT WHEN SAID MOVABLE ARM OCCUPIES SAID FIRST POSITION; A ROTATABLY MOUNTED DRIVE MEMBER FOR OPERATING SAID ROTATABLE ARM; SAID DRIVE MEMBER BEING MOUNTED FOR ROTATION AT A FIRST END THEREOF AND HAVING A ROLLER MEMBER PIVOTALLY MOUNTED THERETO AT A SECOND END THEREOF; SAID DRIVE MEMBER BEING ROTATABLE BETWEEN A THIRD AND A FOURTH POSITION; FIRST CAM MEANS SECURED TO SAID ROTATABLE ARM AND HAVING A CAM SURFACE POSITIONED TO SLIDINGLY ENGAGE SAID ROLLER MEMBER WHEN SAID DRIVE MEMBER ROTATES TOWARD THE FOURTH POSITION TO DRIVE SAID FIRST CONTACT TOWARD SAID SECOND CONTACT; SECOND CAM MEANS PIVOTALLY MOUNTED TO SAID FIRST CAM MEANS AND HAVING A SECOND CAM SURFACE; SPRING MEANS COUPLED BETWEEN SAID FIRST AND SECOND CAM MEANS FOR URGING SAID SECOND CAM SURFACE TOWARD A FIFTH POSITION ADJACENT ONE END OF SAID FIRST CAM SURFACE TO EFFECTIVELY PROVIDE ONE CONTINUOUS CAM SURFACE; SAID SECOND CAM SURFACE SLIDABLY ENGAGING SAID ROLLER MEMBER WHEN SAID ROLLER MEMBER LEAVES SAID FIRST CAM SURFACE AS SAID DRIVE MEMBER MOVES TOWARD THE FOURTH POSITION; BIAS MEANS COUPLED TO SAID ROTATABLE ARM AT SAID FIRST END NORMALLY BIASING SAID FIRST AND SECOND CONTACTS OUT OF ENGAGEMENT. 